An Intrascene Wide Dynamic Range CMOS Image Sensor Using Dual-Gain Ramp Generator for Machine Vision Applications

This study presents an advanced dual-imaging CMOS image sensor (CIS) optimized for intrascene wide dynamic range (WDR) machine vision applications. Based on examining the operational characteristic and structure of traditional ramp signal generator used in CISs, we proposed a new dual-ramp signal generator, enabling the concurrent generation of ramp signals with diverse analog gains (AGs). By employing a top and bottom readout array configuration, the proposed CIS enables the simultaneous conversion of pixel data with differing AGs using the proposed dual-ramp signal generator. This approach enables real-time dual imaging without any modification of standard pixel structures, effectively accommodating varying light intensities while avoiding motion artifacts. To further enhance the image quality, this work presents an efficient two-step pre-emphasis ramping technique. It effectively minimizes the column fixed pattern noise (CFPN) that typically arises due to the inherent gain changes in ramp generators. As a result, this dual-imaging CIS can serve as a promising solution for effective intrascene WDR imaging for machine vision. This prototype CIS with the proposed edge detection counter was fabricated using a 0.11- $\mu $ m CIS process with a pixel resolution of 1280 (H) $\times 720$ (V). The prototype CIS operates with a power consumption of 6.31 mW and achieves a frame rate of 59 frames per second (fps). The prototype CIS demonstrated the figures of merits (FoMs) of 116.1 pJ/frame/pixel, $36.04{\%}\cdot \text {fJ}$ /frame/pixel, and $0.035{\%}\cdot \text {fJ}$ /frame/pixel/ $2^{\text {N}}$ .